Facile synthesis of silver nanoparticles stabilized dual responsive silica nanohybrid: A highly active switchable catalyst for oxidation of alcohols in aqueous medium

Abstract

The design of switchable hybrid systems to control the catalytic activity using stimuli-responsive polymers have a great significance in the precise manipulation of the oxidation reactions. Herein, we proposed a novel and facile approach for the synthesis of a dual-responsive silica nanohybrid catalyst by combining the temperature-responsive poly N-isopropylacrylamide (PNIPAM) and pH-responsive poly 4-vinylpyridine (P(4-VP)) with MCM-41 as integrated support via free radical polymerization. The prepared switchable material was decorated with silver nanoparticles (AgNPs) through the co-reduction approach. The X-ray photoelectron spectroscopy (XPS) data confirmed the existence of AgNPs in the zero oxidation state while the dynamic light scattering (DLS) measurements revealed that the material exists in maximum swelling confirmation at low temperature (<32 °C) and pH (<4). This AgNPs-MCM-41-PNIPAM/P(4-VP) catalyst was used for the catalytic oxidation of alcohols to the corresponding aldehyde and ketones in water medium at room temperature by using periodic acid as the oxidant. Also, the catalyst could be used at least five times without losing its heterogeneity and catalytic activity.